Abstract
Retreat rate of snow in altitude in spring is observed at some stations on Route 112 along two valleys with east to west direction on both sides of Mt. Gassan. Rate of retreat is slow in lower foot, 40-50 days to reach 150 m in altitude, but the rate increases abruptly in higher foot, only about 10 days to reach more than 200 m in altitude. This seems to be similar on both sides of Mt. Gassan, and to be related to the change of daily maximum temperature.
